A rotary member such as a drive shaft, gear and so on used to transmit a torque from a prime mover to a desired portion or a member is vibrated inevitably by a pulsation of the torque or load, or by a friction. A frequency of the vibration is varied according to rotational speed, and high order vibrations such as secondary vibrations are also generated. Therefore, amplitude of vibrations is widened by resonance. As a result, noise is generated and durability of the rotary member is degraded. Examples of a device or mechanism for suppressing such vibrations of equipment for transmitting power by rotation is disclosed in Japanese Patent Laid-Opens Nos. 2010-255853, 11-311309 and 2011-208774.
Japanese Patent Laid-Open No. 2010-255853 describes a torque converter for suppressing a pulsation of a torque from the prime mover, which is arranged on a transmission route of a power from a turbine runner. The torque converter taught by Japanese Patent Laid-Open No. 2010-255853 is comprised of an elastic damper that reduces vibrations by an elastic action of a spring, and a pendulum absorber arranged on a rotary member of an output side of the pendulum absorber. According to the teachings of Japanese Patent Laid-Open No. 2010-255853, torque is transmitted from an output disc connected with the turbine runner to a center housing trough the spring. The center housing is connected with an output shaft and is adapted to be rotated relatively with the turbine runner. In addition, a rolling member is arranged on an outer circumferential side of the center housing while being allowed to oscillate in a circumferential direction of the center housing. According to the teachings of Japanese Patent Laid-Open No. 2010-255853, therefore, the pulsation of the torque from the turbine runner is damped by the elastic damper, and the torque pulse propagated to the center housing is absorbed by the pendulum absorber.
Meanwhile, Japanese Patent Laid-Open No, 11-311309 describes a torque converter comprised of an elastic damper and a pendulum damper. According to the teachings of Japanese Patent Laid-Open No. 11-311309, the pendulum chamber is formed by depressing the end part wall of the converter cover so that the rolling member held therein is allowed to oscillate to suppress the vibrations. In order to lubricate a contact face between the depressed wall and the rolling member oscillating thereon, the oil delivered to the torque converter is applied to the recessed part. In the torque converter taught by Japanese Patent Laid-Open No. 11-311309, the elastic damper suppresses the torque pulse in the power transmitting route from the lockup clutch of the torque converter to the output shaft. Accordingly, the torque pulse transmitted from the prime mover is damped by the pendulum damper, and when the lockup clutch is engaged, the vibrations are suppressed utilizing the elasticity of the elastic damper by transmitting the power inputted to the lockup clutch to the output shaft through the elastic damper.
In turn, Japanese Patent Laid-Open No. 2011-208774 describes a vibration reducing device adapted to suppress pulsation of a torque transmitted from an engine to a torque converter by an elastic damper and a pendulum damper. Specifically, the elastic damper is comprised of a holder rotated integrally with a crank shaft, and a plate to which the power is transmitted from the holder through a spring. Meanwhile, the pendulum damper is comprised of a rolling chamber formed by a rotary member and the plate integrated therewith, and a rolling member held in the rolling chamber while being allowed to oscillate therein. Thus, the vibration reducing device taught by Japanese Patent Laid-Open No. 2011-208774 the torque pulses inputted to the torque converter by the elastic damper and the pendulum damper.
In order to downsize the torque converter, it is preferable to arrange the pendulum damper for suppressing the torque pulse inside of the torque converter. For example, provided that the pendulum damper taught by Japanese Patent Laid-Open No. 2010-255853 is arranged in the torque converter, or that the pendulum damper taught by Japanese Patent Laid-Open No. 11-311309 is employed, the rolling member of the pendulum damper would be soaked by the oil. Therefore, number of oscillations of the rolling member may be changed by viscosity resistance of the oil or by a change in the viscosity resistance depending on an alteration of temperature. Consequently, vibration reducing performance of the damper might be degraded.
The vibration dampening performance of the pendulum damper is changed depending on a mass ratio of the rolling member to the rotary member. Specifically, the vibration dampening performance is improved by increasing a mass of the rolling member to be relatively larger than that of the rotary member. Therefore, if a housing holding the rolling member is integrated with the rotary member whose vibrations are damped by the pendulum damper, as taught by Japanese Patent Laid-Open No. 11-311309, the mass of the housing is added to the mass of the rotary member. Consequently, the mass ratio of the rolling member to the rotary member is reduced to degrade the vibration dampening performance.